1 | initial version |
Your u
variable is a symbolic expression, and the function call syntax with positional/unnamed arguments -- that you use when you write u(x,y,z,t)
-- is deprecated, exactly because it is confusing.
You should write instead
d1 = diff(u,x,t,t,z)
d2 = diff(v,z,z,t,t)
Also, you defined x,y,z,t
as generators of a polynomial ring, but when you substitute them into a symbolic expression (like your symbolic function) they are coerced to symbolic variables of the same name, so you might as well have defined var('x,y,z,t')
.